I have managed to find a HMPrisons document which groups rapists into 3 classifications according to their motives
"Grievance motivated offenders were low in insight and highly suspicious and resentful of others. Their offences were impulsive and vengeful rather than being sexually motivated or planned. Their criminogenic needs were defined as: impulsivity, rape justification, grievance thinking, and an avoidant, negativistic, self-defeating and dependent personality style. Following treatment, this group continued to blame others for their actions. Their level of rape-supportive beliefs and grievance towards women had decreased significantly, and their empathy for their victims improved. Emotional regulation also improved after treatment, but even after the improvement this was still at a problematic level compared to the other groups.
Sexually motivated offenders tended to have planned and fantasised about their sexual offences beforehand. Victims were selected on the basis of expediency, and violence used was instrumental, e.g. to avoid detection. These men were motivated to work on their problems, and were not particularly impulsive, hostile or aggressive. They tended to have stereotypical views about the sexes and believed that a man is entitled to have sex. Following treatment, this group took significantly more responsibility for their offending, their empathy with their victims and their attitudes about rape had improved, and they were better able to regulate their emotions. However, stereotypical views about women, and attitudes about the acceptance of violence against women, had not changed in this group.
Sadistically motivated offenders (sexual murderers only) were fascinated by sexual violence and sexually aroused by thoughts such as death or torture. Their offences were usually planned and tended to involve strangulation, stabbing, mutilation and post-mortem sexual interference. This group did not particularly hold offence-supportive attitudes. They were callous and had shallow emotions and a tendency to angry thinking. Following treatment, this group took more responsibility for their offending and were less likely to ascribe their offences to poor mental health such as depression. Attitudes towards other people in general and to their specific victims were less hostile. Angry thinking had also been reduced in this group"
This is quoted from www.hmprisonservice.gov.uk/assets/.../100013DFSTEP4report(SOTP).doc (hope it works as it opens into a word document)